DESCRIPTION: (Investigator's Abstract): The purpose of the proposed research is to develop and test a novel plethysmographic approach to the determination of human body volume and composition. The need for a practical, accurate, non-invasive and low cost device for the measurement of body composition is well established for the general population and special medical populations. Excess body fat is associated with many disease processes, e.g., cardio-vascular disease, diabetes, pulmonary disease. Insufficient lean muscle mass is gaining recognition as a significant health problem in the elderly. Low birth weight infants often suffer from low caloric and protein reserves. The method is based on analysis of extremely small pressure changes in response to volume perturbation. The procedure is entirely comfortable and minimal patient compliance is required. Further research and development is proposed to refine the approach and validate its use in the general and selected patient populations. Successful development and validation will lead to a new method of body composition assessment that will be highly attractive for commercial application.